From: Will Deacon <will@kernel.org> stable inclusion from stable-5.10.68 commit 35d3ab2ea2ed594406db5cb063dd1f9daf940a83 bugzilla: 182671 https://gitee.com/openeuler/kernel/issues/I4EWUH Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit a69ae291e1cc2d08ae77c2029579c59c9bde5061 upstream. Commit 865c50e1d279 ("x86/uaccess: utilize CONFIG_CC_HAS_ASM_GOTO_OUTPUT") added an optimised version of __get_user_asm() for x86 using 'asm goto'. Like the non-optimised code, the 32-bit implementation of 64-bit get_user() expands to a pair of 32-bit accesses. Unlike the non-optimised code, the _original_ pointer is incremented to copy the high word instead of loading through a new pointer explicitly constructed to point at a 32-bit type. Consequently, if the pointer points at a 64-bit type then we end up loading the wrong data for the upper 32-bits. This was observed as a mount() failure in Android targeting i686 after b0cfcdd9b967 ("d_path: make 'prepend()' fill up the buffer exactly on overflow") because the call to copy_from_kernel_nofault() from prepend_copy() ends up in __get_kernel_nofault() and casts the source pointer to a 'u64 __user *'. An attempt to mount at "/debug_ramdisk" therefore ends up failing trying to mount "/debumdismdisk". Use the existing '__gu_ptr' source pointer to unsigned int for 32-bit __get_user_asm_u64() instead of the original pointer. Cc: Bill Wendling <morbo@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Peter Zijlstra <peterz@infradead.org> Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Fixes: 865c50e1d279 ("x86/uaccess: utilize CONFIG_CC_HAS_ASM_GOTO_OUTPUT") Signed-off-by: Will Deacon <will@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Chen Jun <chenjun102@huawei.com> Acked-by: Weilong Chen <chenweilong@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> --- arch/x86/include/asm/uaccess.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index c9fa7be3df82..5c95d242f38d 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -301,8 +301,8 @@ do { \ unsigned int __gu_low, __gu_high; \ const unsigned int __user *__gu_ptr; \ __gu_ptr = (const void __user *)(ptr); \ - __get_user_asm(__gu_low, ptr, "l", "=r", label); \ - __get_user_asm(__gu_high, ptr+1, "l", "=r", label); \ + __get_user_asm(__gu_low, __gu_ptr, "l", "=r", label); \ + __get_user_asm(__gu_high, __gu_ptr+1, "l", "=r", label); \ (x) = ((unsigned long long)__gu_high << 32) | __gu_low; \ } while (0) #else -- 2.20.1